Low polygon modeling vs good topology
If you care about the real time performance of your model, then forget topology and focus on removing every single unwanted face(poly). You may, when modeling keep good topology in order to expedite and simplify the process. At the end you can go back and remove the remaining extraneous faces before moving onto UV unwrapping and texturing. That is purely a matter of preference. If you don't care about the real time performance, then by all means focus on good topology.